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33 Cards in this Set

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What are the Effects of Adrenergic Antagonists?
A drug which binds to but does not activate an adrenergic receptor is an antagonist at that receptor. Antagonists are also known as receptor "blockers" because they block the effect of agonists and thus antagonists produce "receptor blockade.
Adrenergic receptor antagonists, are all ………….and can be differentiated on ……
- reversibly binding agents at these receptors

- the basis of their relative affinity for the four types of adrenergic receptor.
An adrenergic receptor antagonist has the effect of?
reducing the effects of adrenergic agonists at those receptors and will reduce the influence of the SNS on cells, tissues and organs expressing those receptors and innervated by the SNS.
The most important effects of adrenergic receptors are to?
reduce the influence of the SNS on the heart and blood vessels to reduce cardiac output and to reduce vasoconstriction - and thus to reduce blood pressure, to correct an arrhythmia, or to reduce work performed by (and oxygen demand of) the heart.
What Types of Adrenoreceptor Antagonist are Available?
α Adrenoreceptor Antagonists

Phentolamine (REGITINE) & Prazosin (MINIPRESS)
What is an α Adrenoreceptor Antagonists?
These drugs have low affinity for β adrenoreceptors but have high affinity for one or both types of α adrenoreceptor. These drugs reverse the effects of physiologically active (and clinically administered) epinephrine and norepinephrine mediated through α receptors.
What α adrenoreceptor antagonists are available?


There are two α adrenoreceptor antagonists which you should know about:
Phentolamine (REGITINE) & Prazosin (MINIPRESS)
What is Phentolamine (REGITINE)?
a competitive antagonist at both α1 and α2 adrenoreceptors.
By actions in arterioles of skin and mesentery, phentolamine causes?
vasodilation through effects mediated by α1 adrenoreceptors on smooth muscle in the wall of blood vessels and thus reduces blood pressure; however, this reduction of blood pressure leads to increased cardiac output (increased heart rate) by reflex.
By actions in the GI tract, phentolamine does what?
increases GI motility
Phentolamine is used in?
short term pharmacological control of blood pressure in pheochromocytoma (a condition due to an epinephrine secreting tumor of the medulla of the adrenal gland (which normally requires surgical removal of these glands)) and for which the prime symptom is an excessively high blood pressure & Phentolamine has also been used as an antihypertensive to control high blood pressure in essential hypertension (hypertension caused by an unidentified mechanism).
Problems with Phentolamine?
α2 receptor blockade effectively increases sympathetic tone and produces a number of effects especially tachycardia and arrhythmias potentially leading to angina pectoris and/or myocardial infarction.
What is Prazosin (MINIPRESS)?
a competitive antagonist at α1 adrenoreceptors but has low affinity for all other adrenoreceptors.
Prazosin (MINIPRESS) has all the benefits of phentolamine but does not?
produce the α2 adrenoreceptor mediated, undesired effects of phentolamine.
By actions in arterioles of skin and mesentery, prazosin causes?
vasodilation and thus reduces blood pressure; however, the reduction of blood pressure leads to increased cardiac output (increased heart rate) by reflex (thus reversing the drug’s hypotensive effect).
By actions in the GI tract, prazosin does what?
increases secretions into the GI tract and increases GI motility
Use of prazosin is based on?
its ability to reduce blood pressure.
Prazosin is used to treat?
hypertension resulting from several types of cardiovascular malfunction and to treat essential hypertension.
What are β Adrenoreceptor Antagonists?
These drugs have low affinity for α adrenoreceptors but have high affinity for one or both types of β adrenoreceptor.
These drugs reverse the effects of physiologically active (and clinically administered) epinephrine and norepinephrine mediated through β receptors.
β Adrenoreceptor Antagonists
What β adrenoreceptor antagonists are available?
antagonists at β1 and β2 receptors:
Propranolol (INDERAL)

antagonists only active act β1 receptors:
Metaprolol (LOPRESSOR),
atenolol (TENORMIN),
pindolol (VISKEN)
Propranolol (INDERAL) has high affinity for?
both β1 and β2 adrenoreceptors.
By actions in the heart, propranolol effects it how?
effectively a "cardiac depressant". Propranolol reduces SNS influence on the heart by actions in the S-A node (a negative chronotropic effect; decreased heart rate), at the A-V node (a negative dromotropic effect; decreased rate of conduction through the A-V node) and on cardiac muscle (a negative inotropic effect; decreased contractility of cardiac muscle) to reduce cardiac output and to reduce blood pressure. Reduced cardiac output results in reduced work performed by the heart and thus reduced oxygen use by the heart.
By actions in the kidney, propranolol will ?
cause decreased renin secretion; this effect permits increased urine production with a consequent reduction of blood volume and of blood pressure.
Clinical use of propranolol targets the?
β1 adrenoreceptors of the heart. Reduction of cardiac output is important to reduce blood pressure (in all types of hypertension including essential hypertension) and to reduce work done by the heart (and thus to reduce oxygen use by the heart, thus reversing the oxygen deficit which is the prime mechanistic problem of angina pectoris). Reduction of heart rate, conduction in the A-V node and decreased contractility are also clinically useful effects of propranolol in correcting certain arrhythmias including tachycardia.
The problems to therapeutic use of propranolol are related to?
its effects mediated through β2 adrenoreceptors: the drug tends to produce spasm of the bronchioles and of the arterioles of the heart thus producing asthmatic symptoms and symptoms of angina pectoris (as a result of reduced blood flow to the heart muscle), respectively. The effect to induce symptoms of angina pectoris is ironic considering that propranolol was developed for and is still extensively used for treatment of angina pectoris!!
_____________ are β1 adrenoreceptor selective: these drugs have low affinity for all other types of adrenoreceptors.
Metaprolol (LOPRESSOR), atenolol (TENORMIN), and pindolol (VISKEN)
The advantage of Metaprolol (LOPRESSOR), atenolol (TENORMIN), and pindolol (VISKEN) vs. Propreanolo is?
that they have the advantages of propranolol (with respect to potential therapeutic benefit based on effects in the heart) but not the disadvantages of propranolol (with potential to induce spasm of coronary blood vessels or to induce bronchospasm).
Clinical use of Metaprolol (LOPRESSOR), atenolol (TENORMIN), and pindolol (VISKEN) permits?
reduction of blood pressure (of various types including essential hypertension) and correction of arrhythmias (especially tachycardia) and reversal of oxygen deficit in heart muscle (in angina pectoris).
What drugs are Mixed α and β Receptor Antagonists?
Labetolol (NORMODYNE) and carvedilol (COREDG)
These drugs have affinity for α1, α2 and β1 adrenoreceptors?
Labetolol (NORMODYNE) and carvedilol (COREDG)
Labetolol (NORMODYNE) and carvedilol (COREDG) have combined advantages of what but also their disadvantages like?
propranolol and prazosin (regarding regulation of blood pressure and maintenance of cardiac rhythm) but have retained to some extent the disadvantages of propranolol (regarding bronchospasm and spasm of arterioles of the heart and of skeletal muscle) - the affinity of the drugs for β2 adrenoreceptors is not high.
There are two mixed adrenoreceptor antagonists which you should know about and what do they do?
Labetolol (NORMODYNE) and carvedilol (COREDG) are used to treat hypertension (of multiple causes and including essential hypertension) and certain arrhythmias (especially tachycardia).